The present invention relates generally to methods and apparatus for comminuting materials, particular scrap or waste materials. More particularly, the present invention relates to apparatus, appliances, assemblies or installations having a cutting assembly and to methods of using such equipment in which the cutting assembly reduces the size of the material admitted to the equipment, such as for example by shredding. Even more particularly, the present invention relates to apparatus and methods of using the apparatus in which the cutting assembly comprises two counter-rotating, intermeshing cutting arrays having a plurality of individual cutters in which the tension applied to the cutting arrays is adjustable to take into account wearing of the cutters, particularly by moving an assembly containing the tensioning means with respect to the cutting assembly. Even more particularly, the present invention relates to apparatus having a fixed framework on which is provided the cutting assembly and a movable framework on which is provided the tensioning assembly arranged in such a manner that movement of the movable framework allows adjustment of the tension applied to the cutting assembly by the tensioning assembly. Although the apparatus of the present invention may be used to comminute a wide variety of different materials into pieces of different sizes and shapes, the present invention finds particular application in reducing used tyres to small sized chunks.
Although the present invention will be described with particular reference to an installation for reducing the size of tyres or other waste or recyclable materials, it is to be noted that the scope of the present invention is not restricted to the described arrangement, but rather it is more extensive to include other forms of the equipment, other uses and other methods.
Further, it is noted that although the present invention will be described with reference to a shredder and the process of shredding, the scope of the invention is not limited to shredding but includes other operations of size reduction, such as slicing, cutting and the like.
As time goes by, there is a greater emphasis on recycling waste materials and to be more efficient in the use of recycled materials.
There is also a need to reduce the size of waste material pieces being discharged to landfills, since smaller sized particles or pieces can be compacted into smaller volumes. Currently, it is estimated that up to 30% of the volume of waste material used in landfill is air. By reducing the size of the pieces of waste material, the material can be more closely packed together, thereby reducing or eliminating the amount of voids between individual particles of the waste material when buried in landfills or similar. Thus, if the waste material can be compacted further by reducing its size, the amount of waste material that can be buried as landfill for a given site can be considerably increased, thereby effectively increasing the size of that site without increasing the dimensions of the site.
Further, certain types of waste material can be recycled or used in other operations. For example, discarded tyres can be burnt as fuel or otherwise treated to recover constituent chemicals. In one example, tyres are chopped into pieces and burnt as fuel. However, owing to wire being present in the tyres due to their method of construction, the operation of chopping the tyres into pieces is not entirely successful as the wire resists being broken and causes the individual pieces to be interconnected together. Thus, the individual pieces are not entirely separated from each other. This can cause problems in downstream processing, such as, for example, as contamination in furnaces burning the tyre pieces as fuel, which can block the furnace or contaminate products being formed.
Accordingly, it is an aim of the present invention to address the problems of recycling waste materials and/or to provide an apparatus and method enabling more efficient comminution of materials for any purpose.
According to one aspect of the present invention there is provided a cutting device comprising a fixed framework upon which is mounted a cutting assembly comprising a plurality of cutters and a framework movable with respect to the fixed framework, said movable framework being provided with a tensioning arrangement for maintaining the cutters under tension, wherein the movable framework is movable so as to be selectively positioned with respect to the fixed framework to adjust the tension applied to the cutters, such as for example to take into account wear of the cutters in use.
According to another aspect of the present invention there is provided a shredder comprising a fixed support for supporting two counter-rotating cutting arrays in which each array comprises a plurality of cutters, a movable support upon which a tensioning device is mounted, and an adjustment means interconnecting the fixed support and the movable support, said movable support being movable with respect to the fixed support in response to operation of the adjustment means to adopt a selected position so that tension applied to individual cutters of both arrays is maintained by the tension device at a preselected level, such as for example to take into account wear of the cutters in use.
Typically, the cutters are circular, elliptical, eccentric or other suitable or desirable shape. Typically, there are two cutting arrays, each array comprising a plurality of individual cutters. More typically, the cutters of one array are located intermediate cutters of the other array to form an intermeshing arrangement. Typically, the intermeshing arrangement extends along the length of the cutting arrays.
Typically, the movable support or framework of the present invention includes two plates arranged substantially at right angles to each other. More typically, the vertical plate contains the adjustment means, whereas the horizontal plate contains the or part of the tensioning means. Even more typically, the tensioning means comprises two portions, each portion fixed to respective horizontal plates in which one plate is movable and the other is fixed. One part of the tensioning means applies tension to one array and the other part of the tensioning means applies tension to the other array.
Typically, the two parts of the tensioning means are interconnected by a drive shaft, preferably a telescopic drive shaft, so that movement of the shaft simultaneously controls the amount of tension applied by both parts of the tensioning means.
Typically, the two parts of the tensioning means interconnected by the telescopic shaft are driven by a single motor means, such as for example a hydraulic motor. Even more typically, the same tension is applied to both cutting arrays by two tensioning devices operated by the same hydraulic motor.
Typically, the adjustment means mounted on the vertical plate comprises screw jacks. Typically, the screw jacks are provided with sprockets. More typically, an endless chain collectively engages all sprockets of the screw jacks to simultaneously adjust the position of the movable support or frame with respect to the fixed support or frame. Even more typically, the screw jacks interconnected the fixed framework and the movable framework so that operation of the screw jacks effects movement of the movable framework with respect to the fixed framework, thereby altering the tension applied by the tensioning means.
Typically, each cutting array is supported by one or more bearings. More typically, each cutting array is supported at a location intermediate its ends by the bearing arrangement. Even more typically, each cutting array is supported by the bearing arrangement about the mid-point of each respective array. Even more typically, the bearing arrangement is a slideable bearing arrangement.
Typically, the slideable bearing arrangement comprises an eccentric shaft. More typically, the eccentric shaft oscillates in use to remain clear of the cutting arrays in use. Even more typically, the cutting arrays are provided with individual cutters in which selected ones of the individual cutters contact part of the eccentric shaft to maintain the shaft free of the rotating cutters in use.
Typically, the tensioning device is a coiled torsion spring. More typically, there are two coil torsion springs, one spring for applying tension to one of the arrays, the other spring for applying tension to the other array.
Typically, the cutters are provided with surface irregularities. More typically, the surface irregularities include cleats. Even more typically, one form of the cleat is a plurality of raised blocks located at regularly spaced apart locations around the circumference of the cutter. Even more typically, the cleats are provided with transverse grooves and with circumferentially extending grooves. Even more typically, grooves are provided in the spaces between adjacent cleats. Even more typically, the grooves are axially extending grooves.
Typically, the movable assembly is movable over a linear distance of up to one metre, typically up to 750 millimetres, and more typically up to 600 millimetres.
More typically, the direction of movement is axial with respect to the longitudinal direction of the cutting arrays.
Typically, each cutting array is provided with a drive shaft journalled in a bearing at each end. More typically, the bearing is a multiple bearing comprising at least two bearings arranged in opposed face to face relationship with respect to each other, with one bearing being located within the other, thereby allowing movement of the shaft deviating from alignment along the central axis.